1. Field of the Invention
This application relates generally to repair of flange holes and, more particularly, to methods for repairing holes in flanges of gas turbine engine casings.
2. Description of Related Art
Because engine casing flanges are made to stringent dimensional requirements in terms of I.D. and O.D. dimensions, flatness and hole location, and materials/mechanical performance requirements, the heat input and during the repair and resultant distortion needs to be controlled to prevent flange distortion or a degradation in material microstructure around holes in the flange and mechanical performance.
Casing holes can become oversized in service due to wear or corrosion. Restoration of the inside diameter of small diameter holes is difficult to achieve with conventional fusion welding processes due to weld distortion and mechanical property degradation. One particular type of corrosion is corrosion pitting which has been found in gas turbine engine compressor casing flange bolt holes.
There is, thus, a need for resistance weld repair of casing flange holes that avoids fusion discontinuities and excessive distortion. There is also a need for a weld repair of casing flange holes that minimizes weld distortion while optimizing the microstructure in the repair area to enhance mechanical performance of the flange around the hole.